1. Field of the Invention
The present invention relates to a lens apparatus, in particular to a lens apparatus having a scale ring that rotates about the optical axis in conjunction with driving of a movable optical element.
2. Description of the Related Art
In conventional lens apparatuses that are not provided with a mechanism for adjusting the flange back, the correspondence between actual object distances and scale marks on the focus scale ring is achieved by adjusting the position of the focus scale ring (operating ring) relative to an optical element (or a driving ring for driving the optical element). For example, the lens apparatus disclosed in Japanese Patent Application Laid-Open No. 2003-66304 has a plain scale portion having nothing drawn or inscribed thereon so that scale marks can be drawn on it as desired. The lens apparatus disclosed in Japanese Patent Application Laid-Open No. 2005-128374 has a scale ring that can be rotated to a desired position to allow position adjustment relative to an optical element. Moreover, as a method of allowing adjustment of the fastened position of a cylindrical member, it is known to provide on the cylindrical member an elongated hole through which a screw used to fasten the cylindrical member is attached and to fix the cylindrical member with its position relative to an optical element adjusted in the range of the width of the elongated hole.
In the above-mentioned prior arts, although the position of a scale mark can be set as desired, there is a possibility that the scale mark disappears (or is erased) during operation and/or that the operating ring (scale ring) is displaced relative to the optical element (or driving ring for driving the optical element). This is undesirable for shooting. Moreover, in cases where a fixing arrangement (e.g. an elongated hole) that allows adjustment of the fastening position along the scale direction is provided on the operating ring (scale ring), foreign matters such as dust are liable to enter the fixing arrangement (e.g. an elongated hole) that is exposed to the outside. Furthermore, the lens apparatuses disclosed in the above-mentioned prior arts have only one operating ring for one function (e.g. focusing). Therefore, the techniques disclosed in the above-mentioned prior arts cannot be applied to cases where two operating rings (two scales) whose fastened positions can be adjusted relative to each other are to be used for one function.